Bongo Fury

We've had our 2000 reg Frendee 2.5 l petrol/LPG V6 automatic for a few years, but since last summer it has deveolped an unpredictble fault which means it won't start in the rain, or if it's damp or cold. It tries to but just won't 'catch' as it were. A couple of times the battery's just run out of juice while trying. Occasionally it kicks into life after ages trying. Other times it's all fine as if nothing's wrong. We've changed the distributor unti and the spark plugs. We've had various mechanics look at it, but no-one's the wiser - it's one of those that when it starts everything is fine (runs really well, in fact) but when it won't it won't.
Anyone got any ideas/ tips? I'm not remotely tech-savvy, so please pitch any replies at a very basic level for me!
Thanks.
Simon

Most likely area is the distributor cap itself, then the leads to each spark plug and the king lead to the actual HT generator, these are the parts that are likely to get moist and allow the spark to jump to earth rather than reach the spark plugs themselves.

Thanks - I was assuming getting the distributor unit changed included the cap, but I guess not. I suppose I’d better get someone to go through all those points you mentioned - problem is it’s all fine unless the weather changes, so how does anytime know what the culprit is or how to stop it happening all over again? Is there some sort of weatherproofing, I wonder?

You could use a bottle with a water spray to spray each area and see if anything fails ?

That's a great idea! Thanks.